diff --git a/libcxx/include/numbers b/libcxx/include/numbers
--- a/libcxx/include/numbers
+++ b/libcxx/include/numbers
@@ -73,42 +73,42 @@
 
 namespace numbers {
 
-template <class T>
+template <class _Tp>
 inline constexpr bool __false = false;
 
-template <class T>
+template <class _Tp>
 struct __illformed
 {
-  static_assert(__false<T>, "A program that instantiates a primary template of a mathematical constant variable template is ill-formed.");
+  static_assert(__false<_Tp>, "A program that instantiates a primary template of a mathematical constant variable template is ill-formed.");
 };
 
-template <class T> inline constexpr T e_v =          __illformed<T>{};
-template <class T> inline constexpr T log2e_v =      __illformed<T>{};
-template <class T> inline constexpr T log10e_v =     __illformed<T>{};
-template <class T> inline constexpr T pi_v =         __illformed<T>{};
-template <class T> inline constexpr T inv_pi_v =     __illformed<T>{};
-template <class T> inline constexpr T inv_sqrtpi_v = __illformed<T>{};
-template <class T> inline constexpr T ln2_v =        __illformed<T>{};
-template <class T> inline constexpr T ln10_v =       __illformed<T>{};
-template <class T> inline constexpr T sqrt2_v =      __illformed<T>{};
-template <class T> inline constexpr T sqrt3_v =      __illformed<T>{};
-template <class T> inline constexpr T inv_sqrt3_v =  __illformed<T>{};
-template <class T> inline constexpr T egamma_v =     __illformed<T>{};
-template <class T> inline constexpr T phi_v =        __illformed<T>{};
-
-template <floating_point T> inline constexpr T e_v<T>          = 2.718281828459045235360287471352662;
-template <floating_point T> inline constexpr T log2e_v<T>      = 1.442695040888963407359924681001892;
-template <floating_point T> inline constexpr T log10e_v<T>     = 0.434294481903251827651128918916605;
-template <floating_point T> inline constexpr T pi_v<T>         = 3.141592653589793238462643383279502;
-template <floating_point T> inline constexpr T inv_pi_v<T>     = 0.318309886183790671537767526745028;
-template <floating_point T> inline constexpr T inv_sqrtpi_v<T> = 0.564189583547756286948079451560772;
-template <floating_point T> inline constexpr T ln2_v<T>        = 0.693147180559945309417232121458176;
-template <floating_point T> inline constexpr T ln10_v<T>       = 2.302585092994045684017991454684364;
-template <floating_point T> inline constexpr T sqrt2_v<T>      = 1.414213562373095048801688724209698;
-template <floating_point T> inline constexpr T sqrt3_v<T>      = 1.732050807568877293527446341505872;
-template <floating_point T> inline constexpr T inv_sqrt3_v<T>  = 0.577350269189625764509148780501957;
-template <floating_point T> inline constexpr T egamma_v<T>     = 0.577215664901532860606512090082402;
-template <floating_point T> inline constexpr T phi_v<T>        = 1.618033988749894848204586834365638;
+template <class _Tp> inline constexpr _Tp e_v =          __illformed<_Tp>{};
+template <class _Tp> inline constexpr _Tp log2e_v =      __illformed<_Tp>{};
+template <class _Tp> inline constexpr _Tp log10e_v =     __illformed<_Tp>{};
+template <class _Tp> inline constexpr _Tp pi_v =         __illformed<_Tp>{};
+template <class _Tp> inline constexpr _Tp inv_pi_v =     __illformed<_Tp>{};
+template <class _Tp> inline constexpr _Tp inv_sqrtpi_v = __illformed<_Tp>{};
+template <class _Tp> inline constexpr _Tp ln2_v =        __illformed<_Tp>{};
+template <class _Tp> inline constexpr _Tp ln10_v =       __illformed<_Tp>{};
+template <class _Tp> inline constexpr _Tp sqrt2_v =      __illformed<_Tp>{};
+template <class _Tp> inline constexpr _Tp sqrt3_v =      __illformed<_Tp>{};
+template <class _Tp> inline constexpr _Tp inv_sqrt3_v =  __illformed<_Tp>{};
+template <class _Tp> inline constexpr _Tp egamma_v =     __illformed<_Tp>{};
+template <class _Tp> inline constexpr _Tp phi_v =        __illformed<_Tp>{};
+
+template <floating_point _Tp> inline constexpr _Tp e_v<_Tp>          = 2.718281828459045235360287471352662;
+template <floating_point _Tp> inline constexpr _Tp log2e_v<_Tp>      = 1.442695040888963407359924681001892;
+template <floating_point _Tp> inline constexpr _Tp log10e_v<_Tp>     = 0.434294481903251827651128918916605;
+template <floating_point _Tp> inline constexpr _Tp pi_v<_Tp>         = 3.141592653589793238462643383279502;
+template <floating_point _Tp> inline constexpr _Tp inv_pi_v<_Tp>     = 0.318309886183790671537767526745028;
+template <floating_point _Tp> inline constexpr _Tp inv_sqrtpi_v<_Tp> = 0.564189583547756286948079451560772;
+template <floating_point _Tp> inline constexpr _Tp ln2_v<_Tp>        = 0.693147180559945309417232121458176;
+template <floating_point _Tp> inline constexpr _Tp ln10_v<_Tp>       = 2.302585092994045684017991454684364;
+template <floating_point _Tp> inline constexpr _Tp sqrt2_v<_Tp>      = 1.414213562373095048801688724209698;
+template <floating_point _Tp> inline constexpr _Tp sqrt3_v<_Tp>      = 1.732050807568877293527446341505872;
+template <floating_point _Tp> inline constexpr _Tp inv_sqrt3_v<_Tp>  = 0.577350269189625764509148780501957;
+template <floating_point _Tp> inline constexpr _Tp egamma_v<_Tp>     = 0.577215664901532860606512090082402;
+template <floating_point _Tp> inline constexpr _Tp phi_v<_Tp>        = 1.618033988749894848204586834365638;
 
 inline constexpr double e          = e_v<double>;
 inline constexpr double log2e      = log2e_v<double>;
diff --git a/libcxx/include/optional b/libcxx/include/optional
--- a/libcxx/include/optional
+++ b/libcxx/include/optional
@@ -1167,8 +1167,8 @@
 };
 
 #if _LIBCPP_STD_VER >= 17
-template<class T>
-    optional(T) -> optional<T>;
+template<class _Tp>
+    optional(_Tp) -> optional<_Tp>;
 #endif
 
 // Comparisons between optionals
diff --git a/libcxx/include/type_traits b/libcxx/include/type_traits
--- a/libcxx/include/type_traits
+++ b/libcxx/include/type_traits
@@ -2318,7 +2318,7 @@
 // Clang provides variadic templates in C++03 as an extension.
 #if !defined(_LIBCPP_CXX03_LANG) || defined(__clang__)
 # define _LIBCPP_OPTIONAL_PACK(...) , __VA_ARGS__
-template <class... Tp>
+template <class... _Tp>
 struct __common_types;
 template <class... _Tp>
 struct _LIBCPP_TEMPLATE_VIS common_type;
diff --git a/libcxx/test/configs/apple-libc++-shared.cfg.in b/libcxx/test/configs/apple-libc++-shared.cfg.in
--- a/libcxx/test/configs/apple-libc++-shared.cfg.in
+++ b/libcxx/test/configs/apple-libc++-shared.cfg.in
@@ -13,7 +13,7 @@
     '-isysroot {}'.format('@CMAKE_OSX_SYSROOT@') if '@CMAKE_OSX_SYSROOT@' else ''
 ))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -isystem %{install}/include/c++/v1 -I %{libcxx}/test/support -include %{libcxx}/test/support/nasty_macros.h'
+    '-nostdinc++ -isystem %{install}/include/c++/v1 -I %{libcxx}/test/support'
 ))
 config.substitutions.append(('%{link_flags}',
     '-nostdlib++ -L %{install}/lib -lc++'
diff --git a/libcxx/test/configs/ibm-libc++-shared.cfg.in b/libcxx/test/configs/ibm-libc++-shared.cfg.in
--- a/libcxx/test/configs/ibm-libc++-shared.cfg.in
+++ b/libcxx/test/configs/ibm-libc++-shared.cfg.in
@@ -6,7 +6,7 @@
 
 config.substitutions.append(('%{flags}', ''))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -D__LIBC_NO_CPP_MATH_OVERLOADS__ -isystem %{install}/include/c++/v1 -I %{libcxx}/test/support -include %{libcxx}/test/support/nasty_macros.h'
+    '-nostdinc++ -D__LIBC_NO_CPP_MATH_OVERLOADS__ -isystem %{install}/include/c++/v1 -I %{libcxx}/test/support'
 ))
 config.substitutions.append(('%{link_flags}',
     '-nostdlib++ -L %{install}/lib -lc++ -lc++abi -latomic -Wl,-bbigtoc'
diff --git a/libcxx/test/configs/llvm-libc++-shared-gcc.cfg.in b/libcxx/test/configs/llvm-libc++-shared-gcc.cfg.in
--- a/libcxx/test/configs/llvm-libc++-shared-gcc.cfg.in
+++ b/libcxx/test/configs/llvm-libc++-shared-gcc.cfg.in
@@ -6,7 +6,7 @@
 
 config.substitutions.append(('%{flags}', ''))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -isystem %{include} -isystem %{target-include} -I %{libcxx}/test/support -include %{libcxx}/test/support/nasty_macros.h'
+    '-nostdinc++ -isystem %{include} -isystem %{target-include} -I %{libcxx}/test/support'
 ))
 config.substitutions.append(('%{link_flags}',
     '-L %{lib} -Wl,-rpath,%{lib} -nodefaultlibs -lc++ -lm -lgcc_s -lgcc -lpthread -lc -lgcc_s -lgcc -latomic'
diff --git a/libcxx/test/configs/llvm-libc++-shared.cfg.in b/libcxx/test/configs/llvm-libc++-shared.cfg.in
--- a/libcxx/test/configs/llvm-libc++-shared.cfg.in
+++ b/libcxx/test/configs/llvm-libc++-shared.cfg.in
@@ -7,7 +7,7 @@
     '-isysroot {}'.format('@CMAKE_OSX_SYSROOT@') if '@CMAKE_OSX_SYSROOT@' else ''
 ))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -isystem %{include} -isystem %{target-include} -I %{libcxx}/test/support -include %{libcxx}/test/support/nasty_macros.h'
+    '-nostdinc++ -isystem %{include} -isystem %{target-include} -I %{libcxx}/test/support'
 ))
 config.substitutions.append(('%{link_flags}',
     '-nostdlib++ -L %{lib} -Wl,-rpath,%{lib} -lc++ -pthread'
diff --git a/libcxx/test/configs/llvm-libc++-static.cfg.in b/libcxx/test/configs/llvm-libc++-static.cfg.in
--- a/libcxx/test/configs/llvm-libc++-static.cfg.in
+++ b/libcxx/test/configs/llvm-libc++-static.cfg.in
@@ -7,7 +7,7 @@
     '-isysroot {}'.format('@CMAKE_OSX_SYSROOT@') if '@CMAKE_OSX_SYSROOT@' else ''
 ))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -isystem %{include} -isystem %{target-include} -I %{libcxx}/test/support -include %{libcxx}/test/support/nasty_macros.h'
+    '-nostdinc++ -isystem %{include} -isystem %{target-include} -I %{libcxx}/test/support'
 ))
 config.substitutions.append(('%{link_flags}',
     '-nostdlib++ -L %{lib} -lc++ -lc++abi -pthread'
diff --git a/libcxx/test/libcxx/nasty_macros.compile.pass.cpp b/libcxx/test/libcxx/nasty_macros.compile.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/libcxx/nasty_macros.compile.pass.cpp
@@ -0,0 +1,346 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Test that headers are not tripped up by the surrounding code defining various
+// alphabetic macros.
+
+// Prevent <ext/hash_map> from generating deprecated warnings for this test.
+#if defined(__DEPRECATED)
+#    undef __DEPRECATED
+#endif
+
+#define NASTY_MACRO This should not be expanded!!!
+
+#define _A NASTY_MACRO
+#define _B NASTY_MACRO
+// Windows' <wchar.h> uses _C as an identifier
+#ifndef _WIN32
+# define _C NASTY_MACRO
+#endif
+#define _D NASTY_MACRO
+#define _E NASTY_MACRO
+#define _F NASTY_MACRO
+#define _G NASTY_MACRO
+#define _H NASTY_MACRO
+#define _I NASTY_MACRO
+#define _J NASTY_MACRO
+#define _K NASTY_MACRO
+#define _L NASTY_MACRO
+// FreeBSD's <sys/types.h> uses _M
+#ifndef __FreeBSD__
+# define _M NASTY_MACRO
+#endif
+#define _N NASTY_MACRO
+#define _O NASTY_MACRO
+// MinGW's <wchar.h> uses _P as an identifier
+#ifndef _WIN32
+# define _P NASTY_MACRO
+#endif
+#define _Q NASTY_MACRO
+#define _R NASTY_MACRO
+#define _S NASTY_MACRO
+#define _T NASTY_MACRO
+#define _U NASTY_MACRO
+#define _V NASTY_MACRO
+#define _W NASTY_MACRO
+#define _X NASTY_MACRO
+#define _Y NASTY_MACRO
+#define _Z NASTY_MACRO
+
+// tchar.h defines these macros on Windows.
+#define _UI   NASTY_MACRO
+#define _PUC  NASTY_MACRO
+#define _CPUC NASTY_MACRO
+#define _PC   NASTY_MACRO
+#define _CRPC NASTY_MACRO
+#define _CPC  NASTY_MACRO
+
+// yvals.h on MINGW defines this macro
+#define _C2 NASTY_MACRO
+
+// Test that libc++ doesn't use names reserved by WIN32 API Macros.
+// NOTE: Obviously we can only define these on non-windows platforms.
+#ifndef _WIN32
+#define __allocator NASTY_MACRO
+#define __deallocate NASTY_MACRO
+#define __deref NASTY_MACRO
+#define __full NASTY_MACRO
+#define __in NASTY_MACRO
+#define __inout NASTY_MACRO
+#define __nz NASTY_MACRO
+#define __out NASTY_MACRO
+#define __part NASTY_MACRO
+#define __post NASTY_MACRO
+#define __pre NASTY_MACRO
+#endif
+
+#define __input NASTY_MACRO
+#define __output NASTY_MACRO
+
+#define __acquire NASTY_MACRO
+#define __release NASTY_MACRO
+
+// These names are not reserved, so the user can macro-define them.
+// These are intended to find improperly _Uglified template parameters.
+#define A NASTY_MACRO
+#define Arg NASTY_MACRO
+#define Args NASTY_MACRO
+#define As NASTY_MACRO
+#define B NASTY_MACRO
+#define Bs NASTY_MACRO
+#define C NASTY_MACRO
+#define Cp NASTY_MACRO
+#define Cs NASTY_MACRO
+#define D NASTY_MACRO
+#define Dp NASTY_MACRO
+#define Ds NASTY_MACRO
+#define E NASTY_MACRO
+#define Ep NASTY_MACRO
+#define Es NASTY_MACRO
+#define R NASTY_MACRO
+#define Rp NASTY_MACRO
+#define Rs NASTY_MACRO
+#define T NASTY_MACRO
+#define Tp NASTY_MACRO
+#define Ts NASTY_MACRO
+#define Type NASTY_MACRO
+#define Types NASTY_MACRO
+#define U NASTY_MACRO
+#define Up NASTY_MACRO
+#define Us NASTY_MACRO
+#define V NASTY_MACRO
+#define Vp NASTY_MACRO
+#define Vs NASTY_MACRO
+#define X NASTY_MACRO
+#define Xp NASTY_MACRO
+#define Xs NASTY_MACRO
+
+////////////////////////////////////////////////////////////////////////////////
+// BEGIN-GENERATED-HEADERS
+////////////////////////////////////////////////////////////////////////////////
+
+// clang-format off
+
+// WARNING: This test was generated by generate_header_tests.py
+// and should not be edited manually.
+
+// Top level headers
+#include <algorithm>
+#include <any>
+#include <array>
+#include <atomic>
+#ifndef _LIBCPP_HAS_NO_THREADS
+#    include <barrier>
+#endif
+#include <bit>
+#include <bitset>
+#include <cassert>
+#include <ccomplex>
+#include <cctype>
+#include <cerrno>
+#include <cfenv>
+#include <cfloat>
+#include <charconv>
+#include <chrono>
+#include <cinttypes>
+#include <ciso646>
+#include <climits>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <clocale>
+#endif
+#include <cmath>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <codecvt>
+#endif
+#include <compare>
+#include <complex>
+#include <complex.h>
+#include <concepts>
+#include <condition_variable>
+#ifndef _LIBCPP_HAS_NO_CXX20_COROUTINES
+#    include <coroutine>
+#endif
+#include <csetjmp>
+#include <csignal>
+#include <cstdarg>
+#include <cstdbool>
+#include <cstddef>
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <ctgmath>
+#include <ctime>
+#include <ctype.h>
+#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
+#    include <cwchar>
+#endif
+#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
+#    include <cwctype>
+#endif
+#include <deque>
+#include <errno.h>
+#include <exception>
+#include <execution>
+#include <fenv.h>
+#ifndef _LIBCPP_HAS_NO_FILESYSTEM_LIBRARY
+#    include <filesystem>
+#endif
+#include <float.h>
+#ifndef _LIBCPP_HAS_NO_INCOMPLETE_FORMAT
+#    include <format>
+#endif
+#include <forward_list>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <fstream>
+#endif
+#include <functional>
+#ifndef _LIBCPP_HAS_NO_THREADS
+#    include <future>
+#endif
+#include <initializer_list>
+#include <inttypes.h>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <iomanip>
+#endif
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <ios>
+#endif
+#include <iosfwd>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <iostream>
+#endif
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <istream>
+#endif
+#include <iterator>
+#ifndef _LIBCPP_HAS_NO_THREADS
+#    include <latch>
+#endif
+#include <limits>
+#include <limits.h>
+#include <list>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <locale>
+#endif
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <locale.h>
+#endif
+#include <map>
+#include <math.h>
+#include <memory>
+#ifndef _LIBCPP_HAS_NO_THREADS
+#    include <mutex>
+#endif
+#include <new>
+#include <numbers>
+#include <numeric>
+#include <optional>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <ostream>
+#endif
+#include <queue>
+#include <random>
+#ifndef _LIBCPP_HAS_NO_INCOMPLETE_RANGES
+#    include <ranges>
+#endif
+#include <ratio>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <regex>
+#endif
+#include <scoped_allocator>
+#ifndef _LIBCPP_HAS_NO_THREADS
+#    include <semaphore>
+#endif
+#include <set>
+#include <setjmp.h>
+#ifndef _LIBCPP_HAS_NO_THREADS
+#    include <shared_mutex>
+#endif
+#include <span>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <sstream>
+#endif
+#include <stack>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdexcept>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <streambuf>
+#endif
+#include <string>
+#include <string.h>
+#include <string_view>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <strstream>
+#endif
+#include <system_error>
+#include <tgmath.h>
+#ifndef _LIBCPP_HAS_NO_THREADS
+#    include <thread>
+#endif
+#include <tuple>
+#include <type_traits>
+#include <typeindex>
+#include <typeinfo>
+#include <unordered_map>
+#include <unordered_set>
+#include <utility>
+#include <valarray>
+#include <variant>
+#include <vector>
+#include <version>
+#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
+#    include <wchar.h>
+#endif
+#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
+#    include <wctype.h>
+#endif
+
+// experimental headers
+#if __cplusplus >= 201103L
+#    include <experimental/algorithm>
+#    ifndef _LIBCPP_HAS_NO_EXPERIMENTAL_COROUTINES
+#        include <experimental/coroutine>
+#    endif
+#    include <experimental/deque>
+#    ifndef _LIBCPP_HAS_NO_FILESYSTEM_LIBRARY
+#        include <experimental/filesystem>
+#    endif
+#    include <experimental/forward_list>
+#    include <experimental/functional>
+#    include <experimental/iterator>
+#    include <experimental/list>
+#    include <experimental/map>
+#    include <experimental/memory_resource>
+#    include <experimental/propagate_const>
+#    ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#        include <experimental/regex>
+#    endif
+#    include <experimental/set>
+#    include <experimental/simd>
+#    include <experimental/string>
+#    include <experimental/type_traits>
+#    include <experimental/unordered_map>
+#    include <experimental/unordered_set>
+#    include <experimental/utility>
+#    include <experimental/vector>
+#endif // __cplusplus >= 201103L
+
+// extended headers
+#include <ext/hash_map>
+#include <ext/hash_set>
+
+// clang-format on
+
+////////////////////////////////////////////////////////////////////////////////
+// END-GENERATED-HEADERS
+////////////////////////////////////////////////////////////////////////////////
diff --git a/libcxx/test/support/nasty_macros.h b/libcxx/test/support/nasty_macros.h
deleted file mode 100644
--- a/libcxx/test/support/nasty_macros.h
+++ /dev/null
@@ -1,76 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-#ifndef SUPPORT_NASTY_MACROS_H
-#define SUPPORT_NASTY_MACROS_H
-
-#define NASTY_MACRO This should not be expanded!!!
-#define _A NASTY_MACRO
-#define _B NASTY_MACRO
-#define _C NASTY_MACRO
-#define _D NASTY_MACRO
-#define _E NASTY_MACRO
-#define _F NASTY_MACRO
-#define _G NASTY_MACRO
-#define _H NASTY_MACRO
-#define _I NASTY_MACRO
-#define _J NASTY_MACRO
-#define _K NASTY_MACRO
-#define _L NASTY_MACRO
-// Because FreeBSD uses _M in its <sys/types.h>, and it is hard to avoid
-// including that header, only define _M for other operating systems.
-#ifndef __FreeBSD__
-#define _M NASTY_MACRO
-#endif
-#define _N NASTY_MACRO
-#define _O NASTY_MACRO
-#define _P NASTY_MACRO
-#define _Q NASTY_MACRO
-#define _R NASTY_MACRO
-#define _S NASTY_MACRO
-#define _T NASTY_MACRO
-#define _U NASTY_MACRO
-#define _V NASTY_MACRO
-#define _W NASTY_MACRO
-#define _X NASTY_MACRO
-#define _Y NASTY_MACRO
-#define _Z NASTY_MACRO
-
-// tchar.h defines these macros on Windows.
-#define _UI   NASTY_MACRO
-#define _PUC  NASTY_MACRO
-#define _CPUC NASTY_MACRO
-#define _PC   NASTY_MACRO
-#define _CRPC NASTY_MACRO
-#define _CPC  NASTY_MACRO
-
-// yvals.h on MINGW defines this macro
-#define _C2 NASTY_MACRO
-
-// Test that libc++ doesn't use names reserved by WIN32 API Macros.
-// NOTE: Obviously we can only define these on non-windows platforms.
-#ifndef _WIN32
-#define __allocator NASTY_MACRO
-#define __deallocate NASTY_MACRO
-#define __deref NASTY_MACRO
-#define __full NASTY_MACRO
-#define __in NASTY_MACRO
-#define __inout NASTY_MACRO
-#define __nz NASTY_MACRO
-#define __out NASTY_MACRO
-#define __part NASTY_MACRO
-#define __post NASTY_MACRO
-#define __pre NASTY_MACRO
-#endif
-
-#define __output NASTY_MACRO
-#define __input NASTY_MACRO
-
-#define __acquire NASTY_MACRO
-#define __release NASTY_MACRO
-
-#endif // SUPPORT_NASTY_MACROS_H
diff --git a/libcxx/utils/generate_header_tests.py b/libcxx/utils/generate_header_tests.py
--- a/libcxx/utils/generate_header_tests.py
+++ b/libcxx/utils/generate_header_tests.py
@@ -203,10 +203,9 @@
 
 def main():
     produce_test('double_include.sh.cpp')
-    produce_test('min_max_macros.compile.pass.cpp',
-                 post_include='TEST_MACROS();')
-    produce_test('no_assert_include.compile.pass.cpp',
-                 exclusions=['cassert'])
+    produce_test('min_max_macros.compile.pass.cpp', post_include='TEST_MACROS();')
+    produce_test('nasty_macros.compile.pass.cpp')
+    produce_test('no_assert_include.compile.pass.cpp', exclusions=['cassert'])
 
 
 if __name__ == '__main__':
diff --git a/libcxx/utils/libcxx/test/config.py b/libcxx/utils/libcxx/test/config.py
--- a/libcxx/utils/libcxx/test/config.py
+++ b/libcxx/utils/libcxx/test/config.py
@@ -288,11 +288,6 @@
 
     def configure_compile_flags_header_includes(self):
         support_path = os.path.join(self.libcxx_src_root, 'test', 'support')
-        if self.cxx_stdlib_under_test != 'libstdc++' and \
-           not self.target_info.is_windows() and \
-           not self.target_info.is_zos():
-            self.cxx.compile_flags += [
-                '-include', os.path.join(support_path, 'nasty_macros.h')]
         if self.cxx_stdlib_under_test == 'msvc':
             self.cxx.compile_flags += [
                 '-include', os.path.join(support_path,